Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.35	10.124%	$201.9124	$201.91	$201.90	$201.90
Purchase #2	$76.64	8.409%	$83.0847	$83.08	$83.10	$83.10
Purchase #3	$184.71	13.588%	$209.8084	$209.81	$209.80	$209.80
Purchase #4	$245.71	5.740%	$259.8138	$259.81	$259.80	$259.80
Purchase #5	$80.40	9.787%	$88.2687	$88.27	$88.25	$88.30
Purchase #6	$159.52	8.299%	$172.7586	$172.76	$172.75	$172.80
Purchase #7	$80.68	11.789%	$90.1914	$90.19	$90.20	$90.20
7 purchase totals =	$1,011.01		$1,105.8380	$1,105.83	$1,105.80	$1,105.90